1. Field of the Invention
The present invention relates to an image forming apparatus. More particularly, the present invention relates to a plurality of development cartridges which operate sequentially to form a color image, and an electrophotographic image forming apparatus using the development cartridges.
2. Description of the Related Art
Generally, in an electrophotographic image forming apparatus, light is irradiated onto a uniformly charged photosensitive medium to form an electrostatic latent image corresponding to a desired image, the electrostatic latent image is developed using toner to form a toner image, and the developed image is thereafter transferred and fused onto paper to form the desired image.
Typically, cyan, magenta, yellow and black (CMYK) images are superimposed in a color image forming apparatus to form a desired color image. The color image forming apparatus, therefore, requires four development cartridges to store the four colors of toner, respectively.
A color image forming apparatus including the four development cartridges is not only larger but is more complex than a monochrome image forming apparatus for forming a single color image.
Also, when the development cartridge stores toner, various other components, such as a development roller for developing the electrostatic latent image and the like, are included in the cartridge. After the toner is used up, the development cartridge must be replaced with another development cartridge containing new toner.
The other components, however, have much longer lifespans than the toner, and it is not economical to replace the development cartridge when only the toner has been consumed and the other components still have remaining useful lifespans.
Therefore, there is a need for a method of using the entire development cartridge for its full usable lifespan, in which only additional toner is supplied to the cartridge. This involves separating the toner cartridge and the development cartridge, and supplying new toner by replacing the toner cartridge while using the development cartridge until the end of its lifetime.
When the toner cartridge is detachable from the development cartridge, however, there are problems associated with effectively locating four development cartridges and toner cartridges in the image forming apparatus, and problems associated with reliably supplying the toner stored in the toner cartridge to the development cartridge.
In the latter case, the toner is typically supplied from the toner cartridge to the development cartridge by the free-fall method. In the free-fall method, the toner stored in the toner cartridge falls onto the development cartridge by gravity to supply the toner, and the toner must fall past the components of the development cartridge to reach the development roller.
The toner may not fall directly from the toner cartridge onto the components of the development cartridge, however, and in this case, the distance to the components of the development cartridge becomes long, and the toner is not readily available.
Accordingly, there is a need for an improved development cartridge that can reliably transfer toner from a toner cartridge to a development cartridge.